1. Field of the Invention
The present invention relates to an optical DVI cable, an optical signal transmission equipment and an optical signal transmission system which have the cable, and a method of transmitting optical signal using the cable.
2. Related Background Art
One example of an optical DVI cable based on the Digital Visual Interface (DVI) standard is disclosed in Japan Aviation Electronics Industry, Ltd., Catalog 2003.7 MB-11030-1DVI.pdf. FIG. 6 is a block diagram showing a conventional optical DVI cable together with the host side and monitor side devices. This optical DVI cable includes a transmission module FOJL-DV2(Tx), a reception module FOJL-DV2(Rx), and an electrooptical composite cable (hereafter referred to as a composite cable).
An electrical-optical conversion means (mainly laser diodes) for converting digital video signals input from the host side into optical signals is built into the transmission module. An optical-electrical conversion means (mainly photodiodes) for converting optical signals that have been transmitted from the transmission module into electrical signals is built into the reception module. Power is supplied to the transmission module and reception module by respective dedicated AC/DC adapters that convert a commercial power supply into a direct-current voltage.
The composite cable contains a plurality of optical fibers and a plurality of metal wires. The respective optical fibers transmit the laser signals emitted from the respective laser diodes of the transmission module to the respective photodiodes of the reception module. The metal wires include power supply wires, ground wires, display data channel (DDC) signal wires, and hot plug detect (HPD) wires. The DDC signal wires are used to transmit information from the monitor side to the host side. Furthermore, the DDC signals transmitted by the DDC signal wires include DDC data and a DDC clock. The HPD signals are signals that check the connection state.
In a conventional optical DVI cable, power is supplied by respective dedicated AC/DC adapters for the transmission module and reception module. Accordingly, for example, in cases in which the composite cable has a detachable connector at an intermediate point, a problem arises whereby laser light leaks to the outside during detachment of the connector or in the case of errors in the mounting procedure. Alternatively, there may also be cases in which laser light leaks to the outside as a result of the composite cable being cut in an accident or the like. Lasers used for data transfer do not pose the same danger to humans as lasers that are used for machining. However, since such lasers have high brightness, it is not desirable for the laser light to enter the eyes directly.
Furthermore, the transmission module and reception module used in an optical DVI cable are standardized, and are relatively large in size (width: 39.4 mm, thickness: 15.1 mm, depth of main body part: 57 mm). It is difficult to pass a cable which has such a transmission module and reception module at both ends through ordinary tubing.